Air conditioning system



Feb. 24, 1942. I J. E. ROBB 2,273,992

AIR CONDITIONING SYSTEM Filed March 5, 1937 6 Sheets-Shet l I Inventor Josepk .E. ROBE I jgw Feb. 24-, 1942. 5 055 I 2,273,992

AIR CONDITIONING SYSTEM Filed March 5, 1937 6 Sheets-Sheet 2 Inventor Joseph E Iqbb Feb. 24, 1942. J. E. ROBB 2,273,992

1 AIR CONDITIONING SYSTEM Fil ed March 5, 1957 I 6 Sheets-Sheet 3 Jrzvenzor- Feb. 24,1942; E RO E I 2,273,992

I AI'B- CONDITIONING SYSTEM Fil ed Ma ICh 5, 1937 6 Sheets-Sheet 4 jvzverzfvr .Joseph E 11 01727 9 .J. E. ROBB AIR CONDITIONING SYSTEM Filed March 5, 1937 6 Sheets-Sheet 5 &N

Jflverctor Joseph 3. R0212, B3

e Sheets-Sheet 6 I Inventor Josep'r'z 1 7. 120222.

J. E. ROBB AIR CONDITIONING SYSTEM Filed March 5 1937 Feb. 24, 1942.

Patented Feb.-24, 1942 AIR CONDITIONING SYSTEM Joseph E; Robb, Kansas City, Mo., assignor to Minneapolis-Honeywell Regulator Company, Minneapolis, Minn., a corporation of Delaware Application March 5, 1937, Serial No. 129,201

18 Claims.

This invention relates to air tems.

It is an object of this invention to provide an conditioning sysnovel control arrangements.

More specifically, it is an object of this invention to provide a cooling system for a building having a novel interlocking control arrangement whereby satisfactory and safe operation of the cooling system is assured.

Another object is to provide a novel control arrangement for a plurality of fresh air dampers so that all of the fresh air dampers will be controlled by a single set of controls. Installation and upkeep costs are thereby materially reduced.

A further object is to provide novel control arrangements for a building air conditioning system to maintain desired temperatures within the various zones of the building.

The combining of these novel control arrangements into a single complete air conditioning system that is accurate in its temperature regulation and flexible in operation also form objects of this invention.

Other objects and advantages will become apparent to those skilled in the art upon reference to the accompanying specification, claims and drawings.

For a more thorough understanding of this invention, reference is made to the accompanying drawings in which,

Figure 1 diagrammatically discloses a building having the air conditioning system of this invention applied, thereto;

Figure 2 is a diagrammatic view showing the manner in which the refrigerating apparatus is operated;

Figure 3 is a view showing how the air conditioning apparatus for the first floor is operated;

Figure 4 is a diagrammatic view showing how the cooling coil of the second floor is controlled and how the volume dampers controlling the supply of conditioned air to the second floor are operated;

Figure 5 discloses the manner of controlling the fresh air damper for the second floor; and

Figure 6 discloses the manner of controlling the cooling coil for the third floor, of controlling the volume dampers of the third floor and of controlling the fresh air damper of the third floor by the control mechanism for the fresh air damper of the second floor.

When Figures 2 to 6 are placed end upon end they disclose the complete control system of this invention.

Referring now to Figure 1 there is diagrammatically shown for purposes of illustration a building I0 having a basement H, a first floor air conditioning system for a building having Ill I2, a second floor l3, a third floor l4 and a roof l5. The first floor may have any number of rooms, two of which are shown at I! and I1 and the second and third floors are shown to have rooms l8, I9; 20 and 2|.

Room I6 of the first floor is cooled by a cooling unit generally designated at 23 having a cooling coil in the form of an evaporator 24 and a fan 25 for circulating air over the cooling coil 24. The room ll of the first floor is cooled by a cooling unit generally designated at 26 having a cooling coil 21 in the form of an evaporator and a fan 28 for passing air over the cooling coil 21.

The rooms 18 and IS on the second floor are cooled by an air conditioning unit generally designated at 30. This air conditioning unit includes a cooling coil 3| in the form of an evaporator and air to be conditioned is withdrawn from the spaces or rooms l8 and I9 through a return duct 32. Suitable grills 33 and 34 are provided in the return duct 32 for this purpose. Outside or fresh air is also supplied to the air conditioning unit 30 through an outside or fresh air duct 35. Return air and outside air are drawn through the air conditioning unit 30 over the cooling coil 3| by means of a fan 36 driven by a fan motor 31 and the cooled air is delivered to the spaces l8 and I9 through a supply duct 38. Air from the supply duct 38 is discharged into the room 18 through an inlet 39 and air is also discharged into the room I9 through an inlet Ill.

The supply of outside air to the air conditioning unit 30 is controlled by a fresh air damper 4i The fresh air damper is operated through a crank arm 42, a link 43, and a crank arm H by a proportionlng motor 45. The supply of air to the space I8 is controlled by a volume damper 46 which is operated through a crank arm 41, a link 48 and. a crank arm 49 by a proportionlng motor 50. In a like manner the supply or air to the space H! is controlled by a volume damper 5| operated through a crank arm 52, a link 53 and a crank arm 54 by a proportionlng motor 55.

The air conditioning apparatus for the third floor is in all respects the same as that for the second floor and includes an air conditioning unit 51 having a cooling coil 58 in the form of an evaporator. Return air is supplied to the air conditioning unit 51 through a return air duct 59 having grills so and BI. Outside air is supplied to the air conditioning unit 51 by a fresh air duct 62. A fan 63 circulates the air through the air conditioning unit 51 and this fan is operated by a fan motor 64. The fan 63 discharges air into a supply duct 65 which opens into the spaces 20 and 2! through inlets 66 and 61.

The supply of outside air to the air conditioning unit 51 is controlled by a fresh air damper $8 operated through a crank arm 69, a link II and a crank arm H by a proportioning motor The volume damper I3 which controls the voiume of conditioned air delivered to the space 2% is operated through a crank arm I4, a link IE and a crank arm '50 by a proportionlng motor 5?. In a like manner the volume damper It which controls the supply of conditioned air to the space 2!. is operated through a crank. arm 79, a link 80 and a crank arm II by a proportioning motor 02.

Refrigerant is circulated through the various cooling coils by means of a plurality of compressors, three of which are shown at 05, 06 and it. The compressors as, 00 and 81 are operated by electric motors 08, 09 and 00 respectively. For purposes of illustration it is assumed that the compressor 85 is a two-speed compressor and that when it is operating at low speed it accomplishes 20 tons of refrigeration and when operating at high speed it accomplishes 4!! tons of refrigeration. The compressors 0t and 0'! are single speed compressors and each delivers so tons of refrigeration. The compressors 00, 00 and 81 are connected in parallel and discharge refrigerant into a pipe 0! which leads to condenser 02 located on the roof II. Liquid refrigerant is led downwardly from the condenser 92 on the roof through a. pipe 00. Refrigerant is delivered to the cooling coil 00 of the air conditioning unit 01 on the third floor through a cutof! valve 94 operated by a solenoid motor 00 and expansion valve 00. In a like manner refrigerant is supplied to the cooling coil II of the air conditioning unit 30 of the second floor through a cut off valve 0'! controlled by a solenoid motor 00 and an expansion valve 08. Refrigerant is supplied to the cooling coil 20 of the cooling unit 20 in the space It through a cut-off valve I00 operated by a solenoid motor IOI and an expansion valve I02. Also, refrigerant is supplied to the cooling coil 21 of the cooling unit 20 through a cut-oil valve I03 operated by a solenoid motor I00 and an expansion valve I00. Expanded refrigerant is drawn from the various cooling coils and returned to the compressors 00, 00 and 01 by a suction line I00.

Condensing water is supplied by a pipe I00, pumps I00 and H0 and a pipe III to the condenser 02. Condensing water is discharged from the condenser 02 through a dischar e pipe H2. The pump I00 operates during light refrigerant loads to supply condensing water to the condenser 02 but when the refrigeration load is relatively heavy, pumps I00 and H0, which are in parallel. both supply condensing watcr.to the condenser 02.

The compressor motors 00. 00 and 00 and the condensing water pumps I00 and III are controlled by a step controller ill. The step controller I is in turn operated by a proportioning motor II! which is controlled by a potentlometer type suction pressure controller I II. The suction pressure controller 0 is connected by a pipe III to the suction line 00 leading to the compressors. As the suction pressure increases the various compressors and the condensing water pumps are brought into operation in a predetermined sequence in accordance with the refrigeration load. The manner in which this is accomplished. is specifically shown in Figure 2.

Located in the basement is a panel. board I20 and also on the first, second and third floors are panel boards EM. E22 and I20 respectively. These adjusting the automatic control system which EgDtIOlS the operation of the air conditioning sys- The solenoid motor IOI which operates the valve I00 to control the supply of refrigerant to the cooling unit 23 is controlled by .a space thermostat I25. This thermostat may be of the on and oil type. Space thermostat I 25 maintains the dry bulb temperature of the space I6 at a substantially constant value. The solenoid motor I00 which operates the cut-off valve I03 for the cooling unit 20 is controlled by a thermostatic controller I28 and a humidity responsive controller I21. The thermostatic controller I26 and the humidity responsive controller I21 are of the proportloning type and control the solenoid motor I04 in such a manner as to maintain a substantially constant effective temperature in the space ll. While the effective temperature is maintained substantially constant in the space H the relative humidity in the space I! is allowed to fluctuate.

The volume damper 46 for the room I0 on the second floor is controlled by a thermostatic controller I20 located in the room I0, a humidity responsive controller I20 located in the return air duct 02 and a temperature responsive controller III having bulb I32 located in the. fresh air duct 80. The volume damper 40 is therefore operated in accordance with room temperature} room relative humidity and outdoor temperature to provide a compensated effective temperature control for the space I 0. For a given outdoor temperature a substantially constant effective temperature is maintained within the space Illalthough the relative humidity in the space I8 is allowed to fluctuate. As the outdoor temperature increases the effective temperature of the space I8 is allowed to increase but at a lesser rate. The volume damper 40 is modulated between a minimum open position and a wide open position to accomplish these results. By not completely closing the volume damper l0, circulation of air through the space I0 is at all times provided for ventilation purposes. The volume damper ill for the space I! of the second floor is controlled by a thermostatic controller I23 located in the space II, the humidity responsive controller I00 and the outdoor temperature responsive controller III. Therefore the volume damper II is operated in substantially the same manner as the volume damper 40 for the space I0 so that a compensated effective temperature control is provided for the space I0. The details of construction and mode of operation are more fully disclosed in Figure 4.

The volume damper I0 for the space 20 on the third floor is controlled by a thermostatic controller I located in the space 20, a humidity responsive controller I" located in the return air duct and an outdoor temperature responsive controller I20 having a bulb I01 located in the fresh air duct 02. In a like manner the volume damper 10 for the space 2I is controlled by a thermostatic controller I00 located in the space I2I, the humidity responsive controller I" and the outdoor temperature responsive controller lli. A compensated effective temperature control is therefore provided for the spaces 20 and 2I a detailed showing of which is set forth in Figure 6.

The fresh air damper II for the second floor which is operated by the proportioning motor I is controlled by a temperature controller I40 panel boards have suitable equipment for operat-= s the i c i s system m s f cated in the fresh air duct :5, a temperature reof the. potentiometer type having a bulb Ill 10- 2,273,992 sponsive controller I42 of the on and of! type having a bulb I43 located in the fresh air duct 35 and a humidity responsive controller I44 of both the potentiometer type and the on and oil type located in the fresh air duct 35. The two temperature responsive 'controllers I40 and I42 and the humidity responsive controller I44 all respond to outdoor atmospheric conditions and combine their actions to control the fresh air damper 4I. Specifically. the control contemplated is to maintain the fresh air damper 4I wide open when the wet bulb temperature of the outdoor air is below a given value, say 62 provided the outdoor relative humidity is less than 70 percent and the outdoor dry bulb temperature is greater than 65. However, if the outdoor wet bulb temperature increases above 63 or the outdoor relative humidity increases above '70 percent. or the outdoor dry bulb temperature decreases below 65, the fresh air damper U will be moved to a minimum open position allowing only a minimum amount of outside air to be delivered to the air conditioning unit 80 for minimum ventilation requirements. The minimum open position of the damper 4I may be adjusted to satisfy varying ventilation requirements and also means are provided for completely closing the fresh air damper M in case the fan 36 is not operating. The damper may also be completely closed manually at will. This mode of opersation is more specifically set forth in Figure By means of suitable wiring connections illustrated in Figures 5 and 6 the same set of controls that control the fresh air damper 4I also control the fresh air damper 68 for the third floor and by reason of this installation costs are materially reduced. The control of a plurality of fresh air dampers by a single set of controls is a salient feature of this invention.

Whenever anyof the volume dampers 46 or 5i are moved from the minimum open position toward the wide open position upon a call for cooling, the refrigerant cut-off valve 01 for that zone is opened so that cooling will'be afforded. In a like manner. whenever either of the volume dampers 13 and 18 for the third floor are moved from the minimum open position. the out-off valve 94 is opened to supply refrigerant to the cooling coil 58 for that zone. If no cooling is required for the second floor the volume dampers 46 and 5i move to a minimum open position and the cut-off valve 91 is closed and also if no cooling is required for the third floor the cut-off valve 94 is closed in the same manner. This feature provides an economical mode of operation. If there be no demand for cooling on the second floor and the relative humidity should increase to a predetermined value the cut-oil! valve 91 will be opened by the humidity responsive controller I30 for dehumidifying purposes. In other words, a high limit humidity control is providedfor the second floor. In exactly the same manner a humidity high limit control is provided for the third floor. As stated above. when the demand for cooling is satisfied the volume dampers 46, 5|, 13 and 18 do not entirely close but move to a minimum open position. Under these conditions the air circulates slowly over the cooling coils and the temperature there'- of is reduced below the dew-point and therefore dehumidified. In this manner the relative humidity of the air in the spaces. I8, I8, 20 and 2i 3 may be reduced even though there is no demand for sensible cooling.

Provision is also made for preventing opening of any of the cut-off valves which controlthe supply of refrigerant to the various cooling coils in case none of the compressors are in operation. The purpose of this is to prevent stored refrigerant in the roof condensers 92 under pressure to escape and cool the cooling coilsand to prevent equalizing of the pressures on the high and low side of the refrigerating system. This would tend to fill the compressors in the suction side with refrigerant during periods when the compressors are idle. In other words, a safety interlock is provided to prevent disrupting of the refrigerating system in case the compressors are not operating. The specific manner in which this is accomplished is illustrated in Figure 2 when taken in connection with the remaining Figures 3 to 6. Also the refrigerant cut-off valve of any zone cannot be opened in case the fan of that zone is not operating.

For a more detailed description of how the compressors and the condensing water pumps are operated reference is made to Figure 2. The compressor motors are shown at 88, 88 and and the condensing water pumps are shown at I08 and II 0. The two-speed compressor motor 88 is controlled by a magnetic starter I50 having an operating coil I5I and a magnetic starter I52 having an operating coil I53. When the coil I5I is energized the compressor motor 88 is operated at slow speed to provide 20 tons of refrigeration and when the coil I53 is energized the compressor motor 88 is operated at fast speed to provide 40 tons of refrigeration. The 50 ton compressor motor 88 is controlled by a mangetic starter I54 having an operating coil I55 and the other 50 ton compressor motor is controlled by a magnetic starter I56 having an operating coil I51. The condensing water pump I09 is controlled by a magnetic starter I58 having an operating coil I58 and the condensing water pump II 0 is controlled by a magnetic starter having an operating coil I5I Three phase power is supplied to the compressor motors and the condensing water pumps by means of line wires I62, I63 and I64. It is therefore apparent that when any magnetic starter pulls in its associated pump or compressor motor is placed in operation.

The operating coils of the magnetic starters are controlled by the step controller II 4 which in turn is operated by a proportioning motor H5. The proportioning motor II 8 may be of the type shown in Patent No. 1,989,972 granted to Lewis L. Cunningham on Feb. 5, 1935, or of the type shown in Patent No. 2,028,110 granted to D. G. Taylor on Jan. 14. 1936. The proportioning motor II5 operates a shaft upon which are mounted cams I86 to I15 inclusive. Each of these cams operate switches contacts in a particular sequence.

With the parts In the position shown in Figure 2 the proportioning motor I I5 and consequently the cams operated thereby are in an extreme position. Movement of the proportioning motor II5 away from this extreme position rotates the cams in a clockwise direction: to close and open the various switches in a predetermined sequence. First, the switch arm I16 is moved into engagement'with a contact I11.and the switch arm I18 is moved into engagement with a contact I18; second, switch arm I80 is moved out of engagement with contact I8I and into engagement with contact I82; third, switch'arm I88 moves out comprising switch arms and of engagement with contact its and into engegement with contact 585; fourth, switch am 385 moves into engagement with contact it's; fifth, switch arm I85 moves into engagement with contact 88 and switch arm let moves out of engagement with contact 59! and into engagement with contact 192; sixth, switcharm 5% moves out of engagement with contact I95 and into engagement with contact lilo; seventh, switch arm lSt moves into engagement with contact 557; eighth, switch arm i5 8 moves out or engagement with contact ass and into engagement with contact 209. When the switch arm ass is ultimately moved into engagement with contact 2% the proportioning motor H5 is in the other extreme position. When the proportioning motor 5 i5 is moved from this extreme position to the first extreme position the cams H5 are rotated a counter-clockwise direction and. the same switching action is accomplished except in reverse order.

The proportioning motor H5 is provided with power terminals 265 and Ella which are connected across a secondary 2M of a step-down transformer 2&5 having a primary 2539 connected across line wires 25%) and 2!! leading from some source or power (not shown). The step-clown transformer 298 therefore provides power for the proportloning motor H5. The proportioning motor H5 is also provided with control terminals 212, 25-? and 2M. The control terminal 252 is connected to a switch arm which is adapted to engage contacts N6, 2!? or MS. The suction pressure controller '5. may comprise a slider :ilt adapted to slide across a resistance element 238. The slider 29% and the resistance element form a control potentiometer for the pro portioning motor H5. The slider it is operated by a bellows 222 against the tension of a. spring 2523. The bellows 222 is connected by pipe ii?! to the suction line 533 of the refrigeration apparatus. By adjusting the tension in the spr ng 223 the pressure setting of the suo- 'tion pressure controller lit may be adjusted. The right end of the resistance element 221; and the contact 255 are connected to the control terurinal N3 of the proportiouing motor. In a like manner the left end of the resistance element and the contact 2323 are connected to the control terminal 2M of the proportioning motor H5. contact 251 is connected to the slider 25E: of the suction pressure controller 33%.

-When the switch arm i215 engages the contact 2!! the controller ilfi positions the proportioning motor 1 #5 in a manner well known in the With the slider 2st in the position shown in the drawing the proportioning motor 1 5 is in the extreme position shown in the drawand all of the compressors and the condenser water pumps are shut down. As the slider 12in moves from the right to the left in response to increase in suction pressure the proportloning motor H5 is moved out of the extreme position to perform the above outlined switching action the step controller lit. When the switch error 245 is moved out of engagement with the contact 2 ll automatic control of the proporning motor 535 by the suction. pressure troller i it is prevented. Movement of switch arm into engagement with contact cpthe proportioning motor lit to an stress-e position to move the switches of st 9 conrender all of the compressor motors and the n A- .a. condenser pumps inoperative. Movement of the gara es switch arm 2|5 into engagement with the contact 2i8 operates the proportioning motor US to the other extreme position whereupon the maximum refrigeration tonnage is obtained. Therefore, the switch arm 2 i 5 is capable of placing the refrigerating mechanism under automatic control, of stopping operation of the refrigerating apparatus and of operating the refrigerating apparatus at maximum capacity.

Assume now that the switch arm 215 is engaging the contact 231 whereby the proportioning motor H5 is controlled by the suction pressure controller H5, the suction pressure is low indicating that the compressors need not oper ate. The parts are therefore in the position shown in Figure 2. Upon an increase in suction pressure, the-switch arm HE engages the contact ill andthe switch arm 178 engages the contact 579. A circuit is therefore completed from the line wire 553 through wire 225, switch arm llfi, contact 1 1-7, operating coil Ifiii of the magnetic starter 158 back to the other line wire 58?. This places the pump 3519 in operation. A. circuit is also completed from line wire Hi3 through wire 22$, switch arm lit, contact ill, switch arm I18, contact 79, switch arm i253, contact 184. switch arm 48%), Contact :82, operating coil ii of magnetic starter itlil back the other line wire l52. This places the compressor motor 88 in operation at low speed to supply 23 tons of refrigeration.

Upon a further increase in suction the switch arm it!) is moved out or" with the contact 35 to break the circuit the operating coil l5l of the magnetic sa and is moved into engagement with the contact, 432 to complete a circuit from line Wire it) through'wire 225, switch arm ll' i, COIN/.65 Fl, switch arm H8, contact iii, so itch arm fi l-, contact ill i, switch arm 18? contact it? operating coil 353 of the magnetic 31? back to the other line Wire i Completion of this My. circuit causes operation of the compressor motor 33 at high speed to provide 40 tons of refrigeration.

Upon a further increase in suction pressure switch arm i 33 moves out of engagement with contact lfi to break the circuit the magnetic starter lit whereupon the c mpressor 38 is rendered inoperative and is mo ed into ongagement with the contact- 135 to complete a circuit from the line wire 483 through wire 22d, switch arm lit, contact ill, switch arm lit, c011- taet l'lll, switch arm 3335. contact and operating coil 15! of the magnetic starter hack to the other line wire 3 62. Completion of this circuit pulls in the magnetic starter i5 3 and places the compressor motor 99 in operation whereupon 56 tons of refrigeration are obtained.

Upon a further increase in suction pressure switch arm i315 is moved into engagement with contact i3? to complete a, circuit from line wire :53 through wire 226, switch arm contact lfl'e, switch arm 593, contact i9 3, switch arm 3%, contact 591 and operating coil lot of the magnetic starter i5 1 back to other This circuit pulls in the magnet to operate the compressor mot-or speed to provide additional 2 tons of erstion since both compressors til are at this "time operating, '58 tons of ref tion is provided.

Upon a further increase in suction s h arm its is moved into engagement with so. set 139 and switch arm see is moved out of engagement with contact I 9I and into engagement with contact I92. Movement of the switch arm I90 out of engagement with the contact I9I breaks the circuit through the magnetic starter I50 to stop slow speed operation of the compressor motor 88. Movement of the switch arm I90 into engagement with the contact I92 completes a circuit from the line wire I63 through wire 224, switch arm I86, contact I81, switch arm I93, contact I94, switch arm I90, contact I92 and operating coil I53 for the magnetic starter I52 back tact I89'and operating coil I6I of the magnetic starter I60 back to the line wire I62. Completion of this circuit pulls in the magnetic starter I60 to place the second pump H in operation. Therefore, at this time 90 tons of refrigeration are being provided and both condenser pumps are operating.

Upon a further increase in suction pressure switch arm I93 is moved out of engagement with the contact I94 to break the circuit through the magnetic starter I 52 which stops operation of the compressor motor 88 and is moved into engagement with contact I95 to complete a circuit fromline wire I63 through wire 224, switch arm I86, contact I81, switch arm I93, contact I95 and operating coil I55 of the magnetic starter I54 back to the other line wire I62. Completion of this circuit pulls in the magnetic starter I54 to place the compressor motor 89 in operation. Both compressor motors 89 and 90 are now operating and 100 tons of refrigeration are being provided.

Upon a further increase in suction pressure the switch arm I96 is moved into engagement with the contact I91 to complete a circuit from the line wire I63 through wire 224, switch and I96, contact I91, switch arm I98, contact I99-and operating coil II of the magnetic starter I50, back to the other line wire I62 to cause slow speed operation of the compressor motor 88 to provide an additional tons of refrigeration and since at this time both the compressor motors 89 and 90 are also operating, 120 tons of refrigeration are being provided.

Upon a further rise in suction pressure the switch arm I98 is moved out of engagement with the contact I99 and into engagement with the contact 200. Movement of the switch arm I88 out of engagement with. the contact I99 breaks the circuit through the magnetic starter I 50 to stop slow speed of the compressor motor 88. Movement of the switch arm I 98 into engagement with the contact 200 completes a circuit from the line wire I63 through wire 224, switch arm I96, contact I91, switch arm I98, contact 200 and operating coil I53 of the magnetic starter I52 back to the other line wire I62. Completion of this circuit pulls in the magnetic starter I52 to operate the compressor motor 88 at high speed to provide an additional 40 tons of refrigeration. Since both compressor motors 89 and 90 are also operating at this time, 140 tons of refrigeration are provided.

By reason of the above arrangement upon an increase inrefrigeration load the refrigeration tonnage produced by the refrigerating apparatus is increased in small and graduated steps in the following manner: 20, 40, 50, 70, 90, 100, and tons. This is all accomplished by the use of only three compressors, one of the compressors having two-speed operation. Also when the refrigerating apparatus operates to give 90 tons of refrigeration, both condenser pumps I09 and IIO are operated. In this manner the amount of refrigeration produced by the refrigerating apparatus is modulated in accordance with the refrigerating load so that the correct amount of cooling is at all times maintained in the various cooling coils located on the floors above. Upon a decrease in refrigeration load the suction pressure decreases and the refrigeration tonnage is decreased in the same steps.

-A switch 230 connects a wire 23I with the line wire 2 I0. A switch 232 connects the line wire 2I0 with switches 233, 234, 235 and 236. The switches 233 to 236 are connected in parallel. The switches 233 to 236 control the supply of electrical energy to wires 231, 238, 239 and 240 respectively. A wire 2 is connected to the other line wire 2. The wires 23I, 231, 238, 239, 240 and 24I extend upwardly to the various floors of the building and supply power to the various control instruments and motors on the upper floors. The switches may be located on the control panel I20. The purpose of the switches 230, 232, 233, 234, 235 and 236 will be pointed out more fully hereafter.

Magnetic starters I50, I52, I54 and I56 for the compressor motors 88, 89 and 90 also operate switches 243, 244, 245 and 246 respectively. These switches are connected to the line wire I64 and also are connected in parallel to one end of a relay coil 241, the other end of the relay coil 241 being connected to the line wire I63. The relay coil 241 operates a switch 248 so that when the relay coil 241 is energized the switch 248 is closed to supply power from theline wires I63 and I64 to a primary 249 of a step-down transformer 250 having a'secondary 25I. Since the switches 243,

244, 245 and 246 are connected in parallel and are operated by the magnetic starters, when any compressor motor is placed in operation the relay coil 241 is energized, the switch 248 is closed and power is supplied to the step-down transformer 250. If none of the compressor motors are operating the switch 248 opens and the. supply of power to the step-down transformer 250 is interrupted. The secondary 25I of the step-down transformer 250 is connected to wires 252 and 253 which extend upwardly to the various fioors of the building. The purpose of this arrangement will be pointed out more fully hereafter.

The particular manner in which the control of the cooling units 23 and 26 of the first floor is accomplished is shown in Figure 3. The cut-off valve for controlling the supply of refrigerant to the cooling coil 24 for the space I6 is shown at I00 and the fan for circulating air over this cooling coil is shown at 25. Power is supplied to the fan 25 and the solenoid motor IOI for the cut-off valve I00 by means of line wires 255 and 256 leading from some source of power (not shown). A switch 251 is closed upon energization of a relay coil 258 to cause operation of fan 25, the circuit being completed from the line wire 255 through switch 251, fan 25 back to the other line wire 256. The relay coil 258 is connected across wires 231 and 24I extending upwardly from the basement and when both switches 232 and 233 in thebasement are closed the relay coil 258 is energized and the fan 25 is placed in operation.

The circuit to the solenoid motor IN is controlled by a switch 258 which is closed when a relay coil 260 is energized under the control of the room thermostat generally designated at I25. The room thermostat I25 may include a bellows 25I- containing a volatile fluid responsive to changes in temperature of the space I6. The bellows 26I expands against the tension of a spring 252 to operate a mercury switch 253 to a circuit'closing position upon an increase in temperature above a predetermined value. The temperature setting of the thermostat I25 may be adjusted by adiusting the tension in the spring 252. When the temperature of the space l increases to a predetermined value a circuit is completed from wire 253 through the mercury switch 263 and relay coil 250 back to the wire 252. Completion of this circuit energizes the relay coil 250 to close the switch 259 whereupon the cut-oi! valve I00 isopened to supply refrigerant to the cooling coil 24 of the space I5. Since the power supply for the solenoid motor MI is taken from the fan circuit the cut-oil valve cannot be opened unless the fan 25 is operating and since the power supply for the relay coil 250 is transmitted through the wires 252 and 253 from the transformer 250 in the basement the switch 259 for controlling the solenoid motor IOI cannot be closed 'unless -at least one of the compressor motors is in operation. From this it is seen that upon a call for cooling by the space thermostat I25 the refrigerant cut-off valve I00 is opened providing at least one of the compressor motors is in operation and providing the fan 25 is in operatic Refen'lng now to the upper portion of Figure 3 the method of controlling the temperature of the space l1 on the first floor is shown. The cutoff valve is shown at I03, the fan is shown at 28, the space thermostatic controller at I26 and the space humidity responsive controller at I21. Power is supplied to the fan 28 by line wires 265 and 266. The fan is placed in operation when a switch 251 is closed upon energization of a relay 0011 256. The relay coil 258 is connected across wires 238 and 24I leading from the basement. Therefore, when switches 232 and 234 in the basement are closed the relay coil 258 is energized to close the switch 251 which causes operation of the fan 28. The solenoid motor I04 which operates the cut-oi! valve I03 is controlled by a switch 259 so that when the switch 259 is closed and the fan 28 is in operation the cut-off valve I03 is opened to supply refrigerant to the cooling coil 21 for the space l1. The switch 269 is controlled by a relay generally designated at 210 and this relay is in turn controlled by a relay generally designated at 2". The relay 2" is controlled by the combined action of the space thermostatic controller I26 and the humidity responsive controller I21.

The space thermostatic controller I25 may comprise a bellows 213 containing a volatile fluid and operating against a spring 214 for moving a slider 215 with respect to a resistance element 215. The slider 215 and the resistance element 215 provide a control potentiometer which is adjusted in accordance with variations in space temperature. Upon an increase in space tememtiire the slider :15 is moved to the right in the direction indicated by the character H and upon a decrease in temperature the slider is moved to the left in the direction indicated by the character C. The humidity responsive consive element 211 operates to move the slider 219 to the right in the direction indicated by the character W and-upon a decrease in relative humidity the slider 218 is moved to the left in the direction indicated by the character D.

The relay 21l may comprise relay coils 282 and 283 for operating an armature 284. The armature is connected to a switch arm 285 which is adapted to engage contacts 255 and 281. When the relay coil 262 is energized more than the relay coil 283 the switch arm 255 engages contact 286 and when the relay coil 253 is energized more than the relay coil 282, the switch arm 235 engages the contact 281. The inner ends of the relay coils 282 and 283 are joined together and the outer ends thereof are connected across the wires 252 and 253 which lead from the step-down transformer 250 in the basement. The relay coils therefore are connected in series with respect to each other and across the source of power. The left end of the relay coil 252 is connected through a protective resistance 285 to the left ends of the control potentiometer resistance 215 and the compensating potentiometer resistance 250. In a like manner the right end of the relay coil 283 is connected through a protective resistance 259 to the right ends of the control potentiometer resistance 215 and' the compensating potentiometer resistance 280. The junction of the relay coils 252 and 283 is connected to the slider 215 of the control potentiometer and to the slider 218 of the compensating potentiometer. A variable resistance 280 is connected in series with the slider 219 of the compensating potentiometer to desensitize-the controlling action of the compensating potentiometer. By reason of these wiring connections it is seen that the control potentiometer and the compensating potentiometer are connected in parallel with each other and in parallel with I the series connected relay coils 282 and 283.

The relay generally designated at 210 comprises a relay coil 292 and a relay coil 293 for operating an armature 294. The armature 284 operates the switch 258 and also operates a switch arm 295 with respect to a contact 285. When neither relay coil 292 or 293 is energized the switches 295 and 258 are opened by means of springs, gravity or other means (not shown). When the relay coil 292 is energized the switches 295 and 269 are closed. The relay coil 293 is adapted to counteract the action of the relay coil 292 so that when both relay coils 292 and 293 are energized the switches 295 and 269 are opened by means of springs, gravity or other means (not shown). In other words, the relay pulls in when the relay coil 282 is energized and drops out when both coils 292 and 293 are energized or when neither relay coil 292 or 293 is energized.

With the parts in the position shown in the drawing the slider 215 of the room thermostatic and the relay 210 is out. Upon an increase in space temperature or upon an increase in space relative humidity the slider 215 or the slider 219 is moved to the right to cause partial short circuiting of the relay coil 283 to decrease the energization thereof and to increase the energize.- tion of the relay coil 292. This causes movement. of the switch arm 285 into engagement with the contact 286 to complete a circuit from wire 252 through contact 286, switch arm 285 and relay coil 292 back to the other wire 253. Completion of this circuit energizes the relay coil 292 to close switch 269 and move switch arm 295 into engagement with contact 296. Closure of the switch 289 causes opening of the cut-oil valve I03 providing the fan 28 is operating to supply refrigerant to the cooling coil 21. Movement of the switch arm 295 into engagement with the contact 296 completes a maintaining circuit for the relay coil 292 which may be traced from the wire 252 through switch arm 295, contact 299 and relay coil 292 back to the other wire 253. Therefore the relay coil 292 is maintained energized even though the switch arm 285 be moved out of engagement with the contact 289.

As a result of opening of the cut-off valve in this manner either the space temperature decreases or the space relative humidity decreases to move the slider 215 or the slider 219 to the left. When the slider 215 or the slider 219 has moved suiiiciently far to the left to partially short circuit the relay coil 282, the relay coil 283 becomes more highly energized than the relay coil 282 whereupon the switch arm 285 moves into engagement with the contact 281. This completes a circuit from the wire 252 through switch arm 295, contact 296, switch arm 235, contact 281 and relay coil 293 back to the other wire 253. This causes energization of the relay coil 293 to drop out the relay whereupon the switch arm 295 moves out of engagement with contact 296 and switch 269 opens. The supply of refrigerant to the cooling coil 21 is thus interrupted. Since the relays 21I and 219 are controlled in this manner by both room dry bulb temperature and room relative humidity the solenoid motor I94 is therefore operated in accordance with the eiiective temperature of the space I1 to maintain the efiective temperature substantially constant. Since the controlling action of the humidity responsive controller I21 is desensitized by the variable resistance 219 the cut-off valve I03 is controlled primarily in response to variations in dry bulb temperature which is compensated by variations in space relative humidity. By properly adjusting the variable resistance 210 the effective temperature of the space 2| 1 may be maintained substantially constant although the relative humidity of the space I1 is allowed to fluctuate.

Since the supply of electrical energy to the relays 210 and NI is received from the step-down transformer 250 in the basement it is impossible to pull in the relay 210 in case none of the compressors are operating. It follows then that the cut-oil valve I03 is opened and closed in accordance with the effective temperature of the space I1 but it is impossible to open the cut-off valve I03 if the fan 29 is not operating or if none of the compressors are operating.

Figure 4 shows the manner in which the volume dampers 49 and II, the fan motor 31 and the cut-off valve 91 for the second floor are operated. 'Ilhe proportioning motor 50 which opcrates the volume damper 4B and the proporment 333.

tioning motor 55 which operates the volume damper 5| may be of the type disclosed in Patent No. 2,932,658 granted to W. H. Gille on March 3, 1936. The proportioning motors 59 and -55 are therefore spring returned or power failure type motors. The proportioning motor59 may comprise a shaft 300 for operating the crank arm 49. The shaft 300 is driven through a reduction gear train 30I by a motor rotor 302. The motor rotor 302 is operated by three field windings 303, 304 and 305. The field winding 304 is a holding winding to maintain th motor in any of its adjusted positions. The field winding 305 is an energizing winding and when the windings 394 and 395 are energized the damper 46 is moved towards an open position against the action of a spring 362. The field winding 303 is a bucking winding and when both windings 303 and 304 are energized they neutralize the effect of each other and the spring 362 operates the damper 46 toward a closed position. The shaft 309 operates an abutment member 306 which is adapted to open limit switches 301 and 308 when the motor is moved to either extreme position. The shaft 390 also operates a slider 309 with respect to a resistance element 3I0, the slider and the resistance element forming a balancing potentiometer. The shaft 399 also operates a cam 3I0 which works against; a bell crank lever 3II carrying a mercury switch 3I2. The arrangement is such that when damper 45 is in a minimum open position, the switch 3I2 is opened and when the damper 46 is moved toward. a wide open position from the minimum open position, the switch 3I2 is closed.

The proportioning motor includes a relay generally designated at 3I5. The relay comprises relay coils 3I6 and 3H for operating an armature 3I8. The armature 3I8 in turn operates a switch arm 3I9 with respect to contacts 320 and 32L When the relay coil 3I6 is energized more than the relay coil 3I1 the switch arm 3I9 is moved into engagement with the contact 329. When the relay coil M1 is energized more than the relay coil 3I5, switch arm 3I9 is moved into engagement with the contact 32I. When the relay coils 3I6 and 3H are equally energized the switch arm 3I9 is maintained spaced midway between the contacts 320 and 32I as shown in Figure 4.

The proportioning motor 50 is controlled by the room thermostatic controller I29, the relative humidity responsive controller I30 and the outdoor thermostatic controller I3I. The room thermostatic controller I29 may comprise a bellows 323 containing a volatile fluid for acting against a spring 324 to move a slider 325 with respect to a resistance element 326. The slider 325 and the resistance element 326 form a control potentiometer. Upon an increase in space temperature the bellows expands to move the slider 325 towards the right in the direction indicated by the character H. Upon a decrease in space temperature the slider 325 moves toward the left in the direction indicated by the character C.

The relative humidity responsive controller I30 may comprise a humidity responsive element 321 operating against a spring 328 to rotate a shaft 329. The shaft 329 operates a slider 330 with respect to a resistance element 33I and also a slider 332 with respect to a resistance ele- The slider 339 and the resistance element 33I and the slider 332 and the resistance element 333 form compensating potentiometers.

I V Upon an increasein relative humidity the sliders 338andf332 are movedto rtherlght in the direction indicated by the character W, and upon ;a decrease in relative humidity the sliders 330 containing a volatile fluid and located in the fresh air duct 35. The bellows 335 operates against aspring 336 for operating a shaft 331. The shaft 33! operates a slider 338 with respect to a resistance element 339 and a slider 340 with respect to a resistance element 34!. The slider 338 and the resistance element 339 and the slider 335 and the resistance element 3 form compensating potentiometers. Upon an increase in outdoor temperature the sliders 338 and 340 are moved toqthe left in the directionindicated by the character H and upon a decrease in outdoor temperature the sliders338 and 340 are moved to the right in the direction indicated by the character C.

The room thermostatic controller 133' may comprise a bellows 342 containing a volatile fluid for operating against as spring 34-3 to move a aava ecef 3i7 is connectedto the slider 389 of the balancing potentiometer, the slider 325 of the space therrnostatic controller, the slider 333 of the humidity responsive controller and the slider 338 of the outdoor thermostatic controller. A resistance 35'! is connected in series with the slider 338,

.a resistance 358 is connected in series with the slider 338 and a resistance 353 is connected in series with the slider 393. From the above it is seen that the control potentiometer, the two compensiting otentiometers and the balancing potentiometer are all connected in parallel with the'series connected relay coils Bit and 311 and across the wires 339 and 353.

With the parts in the position shown in Figure 4 the holding Winding 334 of the proportioning motor is energized by reason of a'circuit extending from the wire 343 through switch 351, winding 3%, limit switch 353 and resistance 3B0'back to the other wire 353. Therefore the proportioning motor 55 and the damper 46 are maintained in their adjusted positions against the action of the spring 352. Omitting for the time being the con- I trolling action of the humidity responsive controller 130 and the outdoor thermostatic controller 131, an increase in the temperature of the space it! causes movement of the slider 325 to the slider 344 .with respect to a resistance element (v 355. Upon an increase in space temperature effecting the space thermostatic controller 133 the slider 344 is moved to the right'in the direction indicatedvby the character Hand upon a decrease in space temperature the slider 344 is moved to the left in the direction indicated by the character C.

Power is supplied to the proportioning motors 55 and 55 from a step-down transformer, the primary 341 of which is connected across wires 231 and 241. The secondary 348 of the step-down transformer is connected to wires 349 and 355. The wire 349 is connected to the left end of the relay coil 315 of the motor 50 through a switch 351 and the wire 353 is connected to the right end of the relaycoil 311. In a like manner power is supplied to the proportioning motor through a switch 352. From this it is seen that if the the switch 352 interrupts the supply of power to the proportioning motor 55.

The left end of the relay coil 316 is connected through a protective resistance 353 and a limithis resistance 354 to the left ends of the resist-' ance elements 326, 331 and 335. The right end or the relay coil 31! is connected through a protective resistance 355 to the right ends of the potentiometer resistance elements 325, 331 and 333. The left end of the relay coil 3E5 is also connected through the protective resistance 3-53 to the left end of the,balancing potentiometer resistance element 313 and the right end of the relay coil 3|! is connected through the protective resistance 355 and a resistance 355 to theright end of the balancing potentiometer resistance element. The junction oi the relay coils 315 and right. This decreases the cnergization of the relay coil 3!! and increases the energizatoncf the relay coil 316 to move the switch arm 3i9 into engagement with contact 329. This completes a circuit from the Wire 3453 through switch switch arm 319, contact 323, winding 335 and limit switch 381 back to the other 'wire 356. Both windings 3M and 335 are energized and the motor operates to move the damper 36 toward an open position against the action of the spring 382. Operation of the motor 53 to move the damper 43 towards an open position causes left hand movement of the slider 339 of the balancing potentiometer. This left hand movement of the slider 333 decreases the energization of the relay coil 333 and increases the energization of the relay coil 3i? and when the slider 33:? is moved sufflciently far to the left to rebalance the energizeticn of relay coils 335 and ill? the slider 313 is moved out of engagement with the contact 33K? to break the circuit through Winding 305. Winding 3535 still remains energized and therefore the damper 33 is maintained its newly adjusted position. In this manner damper 5G is 325 is moved toward the left to decrease the energization of the relay coil 3H3 and increase the energiaation of the relay coil 3i? with consequent movement bf the switch arm 3 i 5 into engagement with the contact 32;. This completes a circuit from the wire 3 29 through switch 35!, switch arm 3153, contact 32L bucking winding 333, limit switch 355 and resistance 333 back to the other wire 353. Energization of the field wind ng 333 in this manner neutralizes the holding action of the holding winding 334 end the spring 352 moves the damper towards a closed position. Movementof the damper d8 towards a closed position causes right-hand movement of the slider to decrease the energization of the relay coil 3 i l and increase the encrgization of the relay coil 356. When the slider 2333. has moved sufiiciently far to the right to rebaiance the energizations ofthe relay coils 356 and 3!? the switch arm 31% is moved out of engagement with the contact 321 whereupon the bucking winding 333 is deenergized. Motor 53 and the damper 43 will be maintained in the newly adjusted position since the holding winding 334 remains energized. In this manner the damper 43 is modulated towards a closed position in accordance with the amount of decrease in space temperature.

The variable resistance 359 in series with the slider 333 of the balance potentiometer is utilized for desensitizing the rebalancing action of the balancing potentiometer whereupon movement of the slider 325 of the control potentiometer through the range A will cause complete opening and closing movement of the damper 43. The compensating potentiometer of the humidity responsive controller I33 is connected in parallel with the control potentiometer of the room thermostatic controller I29 and tends to operate the proportioning motor 53 in substantially the same manner as the control potentiometer operates the proportioning motor. Resistance 351 in series with the slider 333 is utilized to desensitize the controlling effect of the humidity responsive device I33 and therefore the humidity responsive device I33 acts to shift the control range A of the control potentiometer of the room thermostat I29. Upon an increase in relative humidity the control range A is moved to the left so that lower temperatures will be maintained within the space I3. Upon a decrease in relative humidity the control range A is moved to the right so that increased temperatures are maintained in the space III. 'In this manner a substantially constant effective temperature is maintained in the space I3 although the relative humidity of the space I3 is allowed to fluctuate.

The compensating potentiometer or the outdoor thermostatic controller l3l is connected in parallel with thecontrol'potentiometer of the room thermostat I29 and by reason of the variable resistance 358 in series with the slider 338 the compensating potentiometer of the outdoor thermostat I3I operates to further shift the control range A of the control potentiometer. Upon an increase in outdoor temperature the coritrol range A is shifted to the right so that h gher temperatures are. maintained in' the space It. Upon a decrease in outdoor temperature. the control range A is shifted to the left so that lower temperatures are maintained in the space. In this manner the eifective temperature of the space I8 is allowed to increase as the outdoor temperature increases and the effective temperature is decreased as the outdoor temperature decreases.

The proportioning motor 55 which operates the damper 5| is controlled in exactly the same manner as the proportioning motor 53 which operates the damper 43 to maintain a substantially constant effective temperature in the space I9 which is adjusted in accordance with variations in outdoor temperature. Therefore a further description of the operation of the volume damper 5| is not considered necessary. However, it is noted at this point that a single relative humidty responsive controller I 33 located in the return air duct and a single outdoor thermostatic controller l3'I having the' bulb I32 located in the fresh air duct compensate both room thermostats I29 and I33 to maintain the desired temperatures within the spaces I8 and I9. 9

The resistance 354 in series with the left ends of the potentiometers controlling the operation of the proportioning motor 53 is utilized to prevent complete closing of the damper 43. in other words the damper 43 cannot be completely closed even though there is no demand for cooling. Therefore, a minimum flow of air through the spaces l3 and I9 for ventilation purposes is provided. The minimum open, position of the damper 43 may be adjusted by adjusting the resistance value of the resistance 354. If, however, the switches 35I and 352 are opened or if the switches 232 and 235 in *the basement are opened the supply of power to the proportioning motors 53 and 55 is interrupted and the springs 332 will move the dampers 43 and 5| to a complete closed position. In this manner a complete shut-down is provided.

Power is supplied to the fan motor 31 of the air conditioning unit 33 by line wires 335, 333 and 331. The supply of power to the fan motor 31 is controlled by a magnetic starter 338 having an operating coil 339. The operating coil 339 is connected across wires'239 and 2 so that if switches 232 and 235 in the basement are closed the operating winding 339 is energized and the fan motor 31 is operated. Opening of either of the switches 232 or 235 in the basement deenergizes the operating winding 339 to drop out the magnetic starter 338 whereupon operation of the fan motor 31 is stopped. Solenoid motor 98 which operates the refrigerant cut-off valve 91 for the air conditioning unit 33 receives its supply of'power from the fan circuit and therefore it the fan 31 is not operating the refrigerant cut-off valve 91 cannot be opened.

Located in series with the solenoid motor 98 is a switch 313 operated by a relay coil 31 I. When the relay coil 3" is energized the switch 313 is closed and the refrigerant cut-off valve 91 is opened providing the fan motor 31 is operating. The relay coil 31I is controlled by the switch 3I2 operated by the proportioning motor 53, by a similar switch operated by the proportioning motor 55 and by the switch 334 operated by the humidity responsive device I33. These three switches are arranged in parallel so that when any one of them is closed the refrigerant cutoff valve 91 is opened. When either of the dampers 43 and 5I are moved from their minimum open position towards the open position the switches operated by the proportioning motors 53 and 55 are closed to energize the relay co l 31I to open the refrigerant cut-off valve 91. If the relative humidity in the return air duct 32 increases to a predetermined high value the refrigerant cut-oil valve 91 is opened regardless of the position of the dampers 43 and 5|. The supply of power to the relay coil 31l is obtained from wires 252 and 253 leading upwardly from the step-down transformer 253 in the basement. Therefore ifthe step-down transformer 253 is not energized it is impossible to close the switch 313. As pointed out above the energization of the step-down transformer 253 is controlled by the compressor starters. Therefore if none of the compressors are operating it is impossible to open the refrigerant cut-off valve 91.

Figure 5 discloses the manner of operating the fresh air damper H for controlling the supply of fresh air to the spaces I8 and I9. The damper H is operated by the proportioning motor 45 which may be the spring returned or power failure type shown and described in Patent No. 2,032,658 granted to W. H. Gille on March 3, 1936. Since the construction of this proportioning motor is exactly the same as the proportioning motor 53 illustrated in Figu e 4 like reference characters have been utilized to indicate the parts thereof. Power is supplied to the propcrtioning motor 48 by wires 349 and 358 leading from the secondary 348 of the transformer illustrated in Figure 4. Therefore, when switches 232 and 235 in the basement are closed and the switch 318 lllustrated in Figure is closed, power is supplied to the proportioning motor 45. Opening of any of these switches interrupts the supply of power to the proportioning motor 45 and the spring 382 moves the damper 4| to a complete closed position in the manner pointed out in connection with the proportioning motor 58 of Figure 4.

The proportioning motor 45 is operated by a relay generally designated at 388. The relay 388 comprises a relay coil 38I for operating a switch arm 382 with respect to contacts 383 and 384.

The arrangement is such that when the relay coil ed the damper 4| is moved to a wide open position. When the relay coil 31 is deenergized the switch arm 382 engages contact 383 and since a resistance 385 is in series with the contact 383 the relay coil 3I8'is only partially short circuited to decrease the energization thereof and increase the energizatlon of the relay coil 3". As a result the damper H is moved toward a closed position by the spring 382, the amount of closing movement of the damper being dependent upon the resistance value of the resistance 385 in series with the contact 383. This insures at all times a minimum supply of fresh air to satisfy ventilating requirements.- By adjusting the resistance value of the resistance 385 the minimum position of the damper 4I may be adjusted. From this it is seen that when the relay 388 is Pulled in the damper 4I assumes a wide open position, when the relay 388 drops out the damper assumes a minimum open position depending upon the value of the resistance 385. When the supply of power to the proportioning motor is interrupted, as by opening switch 318 or switches 232 or 238 in the basement, the damper 4| is completely closed.

The relay 338 is controlled by a relay 381 which may comprise an energizing coil 388 and a bucking coil 338 for controlling the operation of an armature 388. When the relay coil 388 is enerlined the armature 388 operates to move switch arms 38I and 382 into engagement with contacts 333 and 384. When the relay coil 388 is deenerlined or when the relay coil 388 and the relay coil 388 are energized the switch arms 38I and 382 are moved out of engagement with their respective contacts 383 and 384 by means of springs, gravity or other means (not shown).

The relay 381 is in turn controlled by a relay generally designated at 386. This relay 388 may comprise relay coils 381 and 388 for operating an armature 388. Th armature 388 in turn operates a switch arm 488 with respect to contacts when the switch 238 inthc basement is closed the transformer 485 becomes energized and is capable of supplying power to the two relay 381 and 388. The relay coil 381 and 388 are connected in series with respect to each other and across the secondary 481 of the step-down transformer 485. The relay 388 is controlled by the humidity responsive controller I44 located in the fresh air duct 35, the proportioning type thermostat I48 having a bulb I located in the fresh air duct 35 and the on and off type thermostat I42 having a bulb I43 located in the fresh air duct 35. As pointed out above the humidity responsive controller I44 includes a proportioning type controller and an on and off type controller but for purposes of illustration in Figure 5 the humidity responsive controller is shown to comprise two controllers, a proportioning type controller I44 and an on and off type controller I44. The proportioning type humidity responsive controller I44 comprises a humidity responsive element 4"! for acting against a spring 4 to operate a slider 2 with respect to a potentiometer resistance element 4I3. Upon an increase in the relative humidity of the outdoor air the slider 2 moves to the left in the direction indicated by the character W and upon adecrease in relative humidity the slider 2 moves to the right in the direction indicated by the character D. For purposes of illustration it is assumed that the slider 4 I 2 engages the W end of the resistance element 4I3 when the relative humidity is percent and engages the D end when the relative humidity decreases to 20 percent.

The proportioning type temperature responsive controller comprises a bellows 4I5 suitably connected to the bulb I located in the fresh air duct 35. The bellows 4I5 operates against a spring 4I8 to move a slider 1 with respect to a resistance element 8. Upon an increase in out door dry bulb temperature the slider 4" moves to the left in the direction indicated by the character H and upon a decrease in outdoor temperature the slider 1 moves to the right in the direction indicated by the character C. For purposes of illustration it is assumed that the slider 4I1 reaches its extreme left hand position when the dry bulb temperature is 88 and reaches the extreme right hand position when the dry bulb temperature is 68".

The on and off type humidity responsive controller I44 comprises a humidity responsive element 4i8' operating against a spring H I to position a mercury switch 428. The mercury switch is provided with left electrodes 4 and right electrodes 422 the inner electrodes bein common. The mercury in the mercury switch normally bridges the right electrodes 422 but when the relative humidity rises to 70 percent the mercury bridges the left electrodes 42I.

The on and off type temperature responsive controller comprises a bellows 424 suitably connected to the bulb I43 located in the fresh air duct 38. The bellows 424 operates against a spring 425 to position a mercury switch 428. The mercury switch 428 is provided with left electrodes 421 and right electrodes 428 the inner electrodes being common. The mercury in the mercury switch 428 normally bridges the left.

electrodes 421 but. when the outdoor temperature decreases to 65 the mercury bridges the right electrodes 428.

The left end of the relay coil 381 is connected through a protective resistance438 to the left ends of the resistance elements 3 and 4", the outer one of the left electrodes 42I of the mercury switch 420 and the outer one of the right electrodes 428 of the mercury switch 426. The right end of the relay coil 398 is connected through a protective resistance 43I to the right ends of the resistance elements M3 and H8. The slider 4 I 2 of the proportioning type humidity responsive controller I44 is connected through a variable resistance 432 to the slider 4I1 of the temperature responsive controller I40. slider M1 is in turn connected to the outer one of the right electrodes 422 of the mercury switch 420. The inner electrode 422 and the inner electrode 42I are connected together and to the outer electrode 421 of the mercury switch 426. The, irmer electrodes 421 and 428 are connected to the junction of the relay coils 391 and 398. With the parts in the position shown in Figure it is seen that the sliders H2 and 1 are connected to the junction of the relay coils 391 and 398 and therefore the potentiometers of the humidity responsive controller I44 and the temperature responsive controller I40 are connected in parallel with the series connected relay coils 391 and 398 and across the secondary 401.

The relay 396 is therefore controlled by the combined action of outdoor relative humidity and outdoor dry bulb temperature. Upon a decrease in outdoor temperature or upon a decrease in outdoor relative humidity the sliders 4H and M2 are moved to the right to partially short circuit the relay coil 398 to decrease the energization thereof and increase the energization of the relay coil 391. This causes movement of the switch arm 400 into engagement withthe contact 40I to complete a circuit from the left end of the secondary 401 through contact 40I, switch arm' 400 and relay coil 388 back to the right end of the secondary 401. As a result the relay coil 388 is energized to move the switch arms 3! and 392 into engagement with contacts 393 and 394. Movement of the switch arm 39I into engagement with the contact 393 completes a maintaining circuit for the relay coil 388 which may be traced from the left end of the secondary 401 through switch arm 39I, contact 393 and relay coil 388 back to the right end of the sec ondary 401.. In this manner the relay coil 388 is maintained energized even though the switch arm 400 should move out of engagement with contact 40I. Movement of the switch arm 392 into engagement with the contact 394 completes a circuit from the wire 23I through switch arm 392, contact 394 and relay coil 38I back to wire 2. The relay coil 38I is therefore energized and the switch arm 392 is moved into engagement with the contact 384 to open wide the fresh'air damper 4|.

Upon an increase in outdoor relative humidity or an increase in outdoor dry bulb temperature the sliders M2 and 4H move to the left to partially short circuit the relay coil 391 to decrease the energization thereof and increase the energization of the relay coil 398. The switch arm 400 is thereupon moved into engagement with the contact 402 to complete a circuit from the 'left end of the secondary 401 through switch arm 39I, contact 393, switch'arm 400, contact 402 and bucking coil 389 back to the right end of the secondary 401. Both coils 388 and 389 are energized and the switch arms 39I and 392 move out of engagement with their respective contacts 393 and 394. As a result the relay 380 drops out and the fresh air damper 4I moves to a minimum position depending upon the resistance value of the resistance 385.

The

By assuming the outdoor relative humidity limits as '70 percent and percent and the outdoor dry bulb limits as 88 and 68 and by properly adjusting the resistance 432, the two instruments provide a wet bulb temperature control. This will become apparent upon references to a psychometric chart. The arrangement is such that as long as the outdoor wet bulb temperature is below 63 the fresh air damper M will be wide open but when the outdoor wet bulb temperature increases above 63 the fresh air damper 4| will be moved to a minimum position. The wet bulb temperature maintained in the building is usually around 63 and therefore if the outdoor wet bulb temperature is less than 63 it is more efflcient to utilize outdoor air for conditioning purposes than recirculated air. However, if the outdoor wet bulb temperature should be greater than 63 it will be more efiicient to use recirculated air for conditioning purposes. There fore the control of the fresh air damper in this manner gives the most efficient operation of the air conditioning system.

The on and oil? type humidity responsive controller I44 is utilized to operate the fresh air damper 4| to a minimum position when the outdoor relative humidity increases to 70 percent even though the outdoor wet bulb temperature should be below 63. In other words, the humidity responsive controller I44 provides a humidity high limit control. When the outdoor relative humidity rises to '70 percent the circuit between the junction of the relay coils 391'and 398 and the sliders 4H and 4| 2 is broken whereby the controllers I44 and I 40 are rendered inoperative to control the proportioning motor 45. The junction of the coils 391 and 398 is then connected through the left contacts 42I of the mercury switch 420 and through the protective resistance 430 to the left end of the relay coil 391 to substantially completely short circuit the relay coil 391 to move the switch arm 400 into engagement with contact 402. The relays 381 and 380thereupon drop out and the damper M is moved to a minimum position. The on and off type temperature controller I42 is utilized for moving the fresh air damper 4| to minimum position when the outdoor dry bulb temperature decreases to 65 even though the outdoor wet bulb temperature is below 63". When the outdoor dry bulb temperature decreases to 65 the circuit to the sliders M1 and H2 is broken to render the controllers I40 and I44 inoperative to control the proportioning motor 45. Also when the mercury bridges the two right electrodes 428 the relay coil 391 is substantially completely short circuited to move the switch arm 400 into engagement with the contact 402 whereupon the relays 381 and 380 drop out to move the fresh air damper 4| to a minimum position.

By reason of the above arrangement it is see that the fresh air damper is maintained in a wide open position when the wet bulb temperature of the outdoor air is above 63"., when the dry bulb temperature is above 65 and when the relative humidity is less than '70 percent. If the wet bulb temperature increases above 63, if the dry bulb temperature decreases below 65 or if the relative humidity increases above percent the fresh air damper 4| is moved to a minimum position. By opening the switch 230 in the basement the supply of power to the relays 381 and 396 is broken and the damper M is moved to a minimum position. By opening the switch 319 which controls the supply of power to the proportioning motor 45 the motor 45 becomes deenergized and the fresh air damper 4| is completely closed.

Figure 6 discloses the manner in which the volume dampers 13 and 18 and the fresh air damper 68 for the third floor are operated. In addition Figure 6'shows the manner in which the fan motor 64 and the refrigerant cut-ofi valve 94 forthe third floor are operated. The volume dampers 13 and 18 are operated by spring return power failure motors 11 and 12 respectively and the fresh air damper 68 is operated by a spring return power failure type motor 12. These three motors may be of the .type illustrated in Figures 4 and 5. The proportioning motor 11 for the volume damper 13 is operated by a room thermostatic controller I34, a humidity compensator I35 and an outdoor temperature compensator I36 to provide a compensated effective temperature control for the space 26 in exactly the same manner as that type of control is provided for the space I8. Similarly the proportioning motor 82 for operating the volume damper 18 is controlled by a room thermostatic controller I38, humidity compensator I35 and an outdoor temperature compensator I36 to give compensated effective temperature control of the space 2I in exactly the same manner as that type of control is obtained for the space I9. Therefore a further description of the temperature control for the spaces20 and 2| is not considered necessary.

The proportioning motor 12 which operates the fresh air damper 68 is controlled by a relay 456 having a relay coil 45I for operating a switch arm 452 with respect to contacts 453 and 454, the arrangement being similar to that shown in Figure 5. When the relay coil 45I is energized the fresh air damper 68 is moved to a wide open position and when the relay coil 45I is deenergized the fresh air damper 68 is moved to a minimum position as determined by the resistance value of the resistance 455. The relay 456 is controlled by the relay 381 of Figure 5. A wire 435 connects the relay coil 45I of Figure 6 in parallel with the relay coil 38I of Figure so that when the relay 381 is pulled in both relays 386 and 450 are pulled in and therefore both fresh air dampers 4| and 68 are moved to a wide open position. When the relay 381 of Figure 5 drops out both relays 380 and 456 drop out and both fresh air dampers H and 68 are moved to a minimum position. By reason of this arrangement a single set of controls is utilized for operating a plurality of fresh air dampers. Duplication of controls is eliminated and installation costs may be materially reduced.

Power is supplied to the three proportioning motors 11, 82 and 12 by a step-down transformer 446 having the primary 44I connected across wires 246 and 24I. If both switches 232 and 236 in the basement are closed power is supplied to this step-down transformer 446. The three proportioning motors 11, 82 and 12 are connected in parallel across the secondary 442 of the stepdown transformer I46 and in circuit with each proportioning motor 11, 82 and 12 is a switch 443, 444 and 445 respectively whereby the power supplied to each proportioning motor may be individually interrupted so that any one of the dampers may be moved to a complete closed position. By opening the switch 232 or the switch 236 in the basement the supply of power to all of the proportioning motors 11, 82 and 12 is interrupted and all of the dampers on the third floor will be moved to a closed position.

Power is supplied to the fan motor 64 by line wires 466, 46| and 462 and the supply of power to the fan motor 64 is controlled by a magnetic starter 463 having an operating coil 464. The operating coil 464 is connected across wires 246 and 2 so that when-switches 232 and 236 in the basement are closed the operating coil 464 is energized to cause operation of the fanmotor 64. The solenoid motor 95 which operates the refrigerant cut-off valve 84 derives its power from the fan circuit so that the cut-off valve may only be opened when the fan motor 64 is operating. The solenoid motor 95 is controlled by a relay 465 having a relay coil 466 for operating a switch 461. When the relay coil 466 is energized the switch 461 is caused to open the cut-off valve 94 provided the fan motor 64 is operating. The relay coil 466 is operated by switches in the proportioning motors 11 and 82 which control the volume dampers and by a switch operated by the humidity responsive controller I35. These switches are all arranged in parallel so that any one of them may cause opening of the cut-off valve. This arrangement is exactly the same as the arrangement for the second floor and therefore a further description is not considered necessary. Power is supplied to the relay coil 466 by wires 252 and 253 leading upwardly from the step-down transformer 256 located in the basement. Therefore the relay 465 may be pulled in only when at least one of the compressors is operating.

From the above it is seen that I have provided an air conditioning system for a building incorporating novel control arrangements. The combining of these novel control arrangements into a single complete air conditioning system provides an air conditioning system that is accurate in its temperature regulation and extremely flexible in its operation.

Although for purposes of illustration I have shown one form of this invention, other forms thereof may become apparent to those skilled in the art upon reference to this specification and therefore this invention is to be limited only by the scope of the appended claims and prior art.

I claim as my invention:

1. In an air conditioning system, the combination of a cooling means, fan means for circulating air in contact with the cooling means and into a space to be cooled, damper means for controlling the volume of air so circulated, means responsive to variations in space temperature for controlling the damper means, valve means for controlling the supply of cooling, fluid to the cooling means, means for opening the valve means as the damper means is moved toward an open position, and means for preventing opening of the valve means in case the fan means is not operating. I

2. In an air conditioning system, the combination of a cooling means, fan means for circulating air in contact with the cooling means and into a space to be cooled, damper means for controlling the volume of air so circulated, means responsive to variations in space temperature for controlling the damper means, valve means for controlling the supply of cooling fluid to the cooling means, means for opening the valve means as the damper means is moved toward an open position, means responsive to space relative humidity for opening the valve means independently of the operatiorf'of the damper means, and means for preventing opening of the valve means in case the fan means is not operating.

.. 3. In an air conditioning system, the combinainto a space to be cooled," damper means for controlling the volume of air so circulated, means responsive to variations in space temperature for controlling the damper means, a cooling apparatus for supplying cooling fluid to the cooling means, valve means controlling, the supply of cooling fluid to the cooling means, means for opening the valve means as the damper means is moved toward an open position, and means for preventing opening of the valve means in case the fan means or the cooling apparatus is not operating.

4. In an air conditioning system, the combination of a cooling means, fan means for circulating air in contact with the cooling means and into a space to be cooled, damper means for controlling the volume of air so circulated, means responsive to variations in space temperature for controlling the damper means, a cooling apparatus for supplying cooling fluid to the cooling means, valve means controlling the supply of cooling fluid to the cooling means, means for opening the valve means as the damper means is moved toward an open position, means responsive to space relative humidity for opening the valve means independently of the operation of the damper means, and means for preventing opening of the valve means in case the fan means or the cooling apparatus is not operating.

5. In an air conditioning system for a building having a plurality of zones, the combination of an air conditioning unit for each zone, a duct for each air conditioning unit for admitting outdoor air to that air conditioning unit, a damper in each duct for controlling the admission of outdoor air to the air conditioning units, and control means associated with one of the air conditioning units for controlling all of the dampers.

6. In an air conditioning system for a building having a plurality of zones, the combination of an air conditioning unit for each zone, a duct for each air conditioning unit for admitting outdoor air to that air conditioning unit, a damper in each duct for controlling the admission of outdoor air to the .air conditioning units, automatically operated control means associated with one of the zones for opening all of the dampers when the admlsison of outdoor air is indicated, and means for closing any of the dampers at will independently of the automatically operated control means.

7. In an air conditioning system for a building having a plurality of zones, the combination of an air conditioning unit for each zone, a duct for each air conditioning unit for admitting outdoor air to that air conditioning unit, a damper in each duct for controlling the admission of outdoor air to the air conditioning units, control means associated with one of the air conditioning units forcontrolling all of the dampers, a cooling means in each air conditioning unit, a cooling apparatus for-supplying cooling fluid to all of the cooling means, a valve for each cooling means for controlling the supply of cooling fluid to the cooling means, thermostatic control means in eaEh zone for controlling the valve of that zone to maintain desired temperature conditions in each zone, and means for preventing Op ning of any of the valves in case the cooling apparatus is not operating.

8. In an air conditioning system for a building having a plurality of zones, the combination of an air conditioning unit for each zone, a duct for each air conditioning unit for admitting outdoor air to that air conditioning unit, a damper in each duct for controlling the admission of outdoor air to the air conditioning units, control means associated with one of the air conditioning units for controlling all oi the dampers, a cooling coil in each air conditioning unit, a plurality of compressors-for supplying cooling fluid to all of the cooling coilsv and for withdrawing expanded refrigerant therefrom, means responsive to suction pressure for placing in operation the compressors in a predetermined sequence as the suction pressure increases, a valve for each cooling coil for controlling the supply of refrigerant to the cooling coils, thermostatic means in each zone for controlling the valve 01 that zone to maintain desired temperature conditions in each zone, and means for preventing opening of any of the valves in case none of the compressors are operating. I

9. In an air conditioning system, the combination of a cooling means, fan means for circulating air in contact with the cooling means and for delivering cooled air to a space to be conditioned, damper means for controlling the volume of air delivered to the space, control means responsive to dry bulb temperature and relative humidity ofthe space for modulating the damper means between a minimum open position and a wide open position to maintain desired effective temperatures in the space but allowing the relative humidity to fluctuate, valve means controlling the supply of cooling fluid to the cooling means, means controlled by the damper means to close the valve means when the damper means is moved to a minimum open position and to open the valve means when the damper means moves away from the minimum open position toward the wide open position, and means operative when the space relative humidity increases to a predetermined value for opening the valve means even though the damper means is in a minimum open position.

10. In an air conditioning system, the combination of cooling means, ian means for circulating air in contact with the cooling means and into a space to be cooled, volume damper means for controlling the volume of air so circulated, means responsive to variations in space temperature for controlling the volume damper means, mechanism for supplying cooling fluid to the cooling means, means operated upon movement of the volume damper means toward an open position for controlling the mechanism to supply cooling fluid to the cooling means, and means operative upon stopping of the tan means for controlling the mechanism to stop the supply of cooling fluid to the cooling means irrespective of the operation of the volume damper means.

11. In an air conditioning system, the combination of cooling means, fan means for circulating air in contact with the cooling means and into a space to be cooled, volume damper means for controlling the volume of air so circulated, means responsive to variations in space temperature for controlling the volume damper means, mechanism for supplying cooling fluid to the cooling means, means operated upon movement of the volume damper means toward an open position for controlling the mechanism to supply cooling fluid to the cooling means, .means responsive to space relative humidity for controlling the mechanism independently of the operation of the volume damper means to supply cooling fluid to the cooling means when the space relative humidity increases to a predetermined value, and means operative upon stopping of the fan means for controlling the mechanism to stop the supply of cooling fluid to the cooling means irrespective of the operation of the volume damper means and the controllingaction of the relative humidity responsive means.

12. In a refrigerating system having an evaporator for cooling 9, medium, a condenser and a compressor, the combination of, control means responsive to suction pressure for starting and stopping operation of the compressor for mainmaintain the temperature of the medium within taining the suction pressure within desired limand means operative upon stopping of the compressor by said control means for closing the valve means regardless of the controlling action of the thermostatic means.

13. In a refrigerating-system having a condenser, a compressor and a plurality of evaporators for cooling a medium, the combination of,

control means responsive to suction pressure for starting and stopping operation of the compressor for maintaining the suction pressure within desired limits, valve means associated with each evaporator for controlling the flow of refrigerant through itsassociated evaporator, thermostatic means associated with each evaporator and responsive to the temperature of the medium being cooled thereby for controlling the valve means of that evaporator to maintain the temperature of the medium within desired limits, and means operative upon stopping of the compressor by said control means for closing all of the valve means regardless of the controlling action of the thermostatic means.

14. In an air conditioning system, the combination of, cooling means in the form of an evaporator, fan means for passing air in contact with the cooling means and into a space to be cooled, a compressor for supplying refrigerant to the cooling means and withdrawing refrigerant therefrom, control means responsive to suction pressure for starting and stopping operation of the compressor for maintaining the suction pressure within desired limits, .valve means for controlling the flow of refrigerant through the cooling means, thermostatic means responsive to space temperature for controlling the valve means to maintain the space temperature within desired limits, and means operative upon stopping :of the compressor by said control means and uponstopping of the fan means for closing the valve means regardless of the controlling action of the thermostatic means.

15. In a refrigerating system having a condenser. a plurality of evaporators for cooling a medium and a plurality of compressors for supplying refrigerant to the evaporators and for withdrawing refrigerant therefrom, the combination of, control means responsive to suction pressure for starting and stopping operation of desired limits, and means operative upon stopping of all of the compressors by said control means for closing all of the valve means regardless of the controlling action of the thermostatic means.

16; In a mechanical refrigerating system, the combination of, evaporator means, a plurality of compressors of different capacities for supplying refrigerant to the evaporator means and for withdrawing refrigerant therefrom, control means responsive to variations in a demand for increased compressor capacity, and switching means operated by'said control means upon a progressive increase in said demand for selectively starting and stopping the various compressors singly or in combinations to increase the total compressor capacity in a number of steps'exceeding the number of compressors.

17. In an air cooling apparatus for a plurality of enclosures, the combination of a plurality of evaporators for respectively cooling the air for the enclosures, means responsive to the temperature of the air in the enclosures for controlling the operation of their respective evaporators, a plurality of refrigerant compressors connected in parallel for supplying liquid refrigerant for' the evaporators, means responsive to a condition the value 01' which normally varies upon variation in the total capacity of the evaporators that are controlled to operate, means controlled by said responsive means for eifecting operation of a portion of the compressors when. said condition is at a first predetermined value, means controlled by said responsive means for effecting operation of a second portion of the compressors of greater capacity than the first portion when said condition is at a second predetermined value, and means controlled by said responsive means and operative when said condition is at a third predetermined value for effecting operation of all of the compressors.

18. In an air conditioning apparatus for a plurality of enclosures, the combination of a plurality of evaporators for respectively cooling the air for the enclosures, a plurality of compressors of various capacities for supplying liquid refrigerant to the evaporators, means responsive to a condition of the air in the enclosures for controlling the flow of refrigerant to the respective evaporators, an electrical control circuit, means normally influenced by the operation of the various refrigerant flow controlling means for varying a characteristic of said electrical circuit, a device connected in the electrical circuit, responding to said characteristic of the circuit and movable to various positions corresponding to various values of said characteristic, means effective in one position of the device for initiating operation of a low capacity compressor, means effective in a second position of the device for terminating operation of the low capacity compressor and for initiating operation of a high capacity compressor and means efiective in a third position of the device for effecting operation of both of the compressors.

JOSEPH E. ROBE. 

